The growth which the computer and electronics industries have experienced in the last three decades has dramatically increased the demand for conductive networks (for example, printed circuit boards (PCB's)). Manufacturers have responded to this demand by increasing the reliability of their products and by packing more electronics into smaller packages. This requires the use of more densely packed electrical modules and circuits, each requiring multiple interconnections to one another. This requirement to increase printed circuit (PC) board density to accommodate yet another generation of new high power integrated circuit (IC) chips, combined with the requirement to incorporate surface mount technology, continues to drive PC board density to new levels of sophistication. However, there is a practical limit to the density that can be achieved using conventional circuit board connectors.
To perform their defined functions, PC boards must be interconnected electrically to other modules and PC boards within a product. This is often accomplished by means of a flexible printed circuit or jumper cable. These jumpers offer users a unique combination of features, namely, they are reliable, they have unique terminating capabilities, they accommodate surface mount requirements and they are extremely lightweight and flexible. Most importantly, such jumper circuits are capable of very high density. Because of these attributes, users have been willing to pay the relatively high cost of such jumper circuits (due to a high rejection rate) and to suffer the inconvenience and expense of hard soldering these jumpers to the PC boards and modules with which they interconnect.
There is a great need for high quality, low cost, densely packed interconnect cables and equally densely packed connector clusters for coupling the cables to the surface mounted terminals of PC boards and modules. In a typical present day application, a floppy disk drive may require a flexible connection to a recording head whose conductors are only on the order of 0.008 inches on center. This means that the jumper's conductors must have a similar spacing. Also, the new liquid crystal displays have conductors which are even more closely packed (for example, 0.004 inches on center) and which must be interconnected to other PC boards and modules. Still further, there is growing use of ceramic PC boards to accommodate multiple IC chip arrays which also require high density connectors and customer interconnect cables for purposes of terminating those components.
As a direct result of the growth in the circuit board industry, there has been a parallel increase in the volume of environmentally-hazardous chemicals generated by the conventional etching and deposition processes. For example, it is not uncommon for one circuit board fabrication facility to generate 1,000 gallons per day of photoresist stripper and 1,200 gallons per week of developer solution. These toxic wastes must be transported off-site for proper disposal at hazardous waste management sites. Thus, there is an urgent need for a non-chemical method for the manufacture of conductive networks.
It is an object of this invention to provide a relatively inexpensive, high-quality, densely packed, conductive network for use in fabricating rigid or flexible circuit boards, that can be built without the use or generation of environmentally hazardous chemicals.
Another object of the invention is to provide a flexible conductive network having conductive paths which are profiled to self-align with corresponding conductors of other conductive networks. A further object of the invention is to provide contact clusters which can be configured to substantially any shape.
Still another object of the invention is to provide a connector assembly with densely packed contact clusters having the self-aligning capabilities.
A further object of the invention is to provide a connector assembly having contact clusters attached which significantly increase the number of signals that each contact position can interconnect and which are specially profiled to align and to interlock with the conductive paths of networks to which they are connected.
Yet another object of the invention is to provide methods of making conductive networks and contact clusters having one or more of the above advantages.